Cardiovascular disease is the leading cause of deaths in the United States, claiming nearly twice as many lives as cancer. While more than 42 million Americans suffer from one or more forms of heart disease, 4.5 million have coronary heart disease, 1.5 million suffer an acute myocardial infarction, and an estimated 500,000 die from coronary artery disease each year. Laser angioplasty has immense appeal but a reliable, predictable system has not yet been developed. The Massachusetts General Hospital and Candela Corporation have conducted preliminary studies to demonstrate preferential absorption of dye laser energy by atheromatous plaques with minimal absorption by normal arterial wall. Candela proposes to investigate the operating parameters of energy, density and pulsewidth to further optimize the selective absorption process in arterial plaques. Specifically we propose to conduct in vitro studies of dye laser plaque ablation in the long pulse, millisecond and short pulse, submicrosecond regimes in order to maximize plaque ablation efficency for various types of commonly occurring plaque types while minimizing irreversible damage to the underlying vascular tissue. If successful animal studies will be undertaken to establish the safety and efficacy of the treatment technique in Phase II. Candela will also pursue design and development of a clinical system in Phase II.